Adriaan, thanks for your response. As for the feature not working "at all", I tested it and found it worked pretty well, but I accepted that it was incomplete and that there might be a surprise or two in store. There are other experimental features in Scala 2.10 that were in common use (e.g. macros), so I assumed that you guys were working on finishing the job. C'est la Vie.
So, you've removed it. Fine - I accept that. However, going back to my original comment, is there any proposed alternative functionality (provide references that are guaranteed not to be null)?
Also, I'm curious: what were the difficulties/holes in implementing this feature?